You don't need to have anything tight against each end of the outer tube. If the column has u/js in it, pulling or pushing on the steering wheel will only try to move the column to one side (which you can't do because of the bearings in which the inner column runs) – you can't compress the u/j or the lower part of the column, or make it stretch, so nothing moves.
Thanks Keith,
That makes sense.
Thanks Micke also, great pics
Lee